As is well known in the art, books are comprised of signatures which are folded sheets bearing the printed matter. The individual signatures which comprise the book or magazine are fed from hoppers or pockets which are an integral component of a packer box. Usually, the signatures for each book are collected one atop another after which they are joined into a book by stitching or the like.
In the usual case, a binding line will have a large number of packer boxes with a variety of different signatures. Selected binding on the basis of demographics has now become an important requirement whereby a customized book may be bound for each individual subscriber by means of demographic controls through a control tape or other computer software. In this manner, it is possible to limit advertising to a demographically selected constituency to ensure maximum impact for the advertiser in a given book.
For this reason, it is necessary to exert control over each packer box. Thus, in a given run of a binding line, there must be constant enabling and disabling of vacuum signature feeding devices from any group of packer boxes. For this purpose, there have been two principal means for controlling the operation of a packer box.
Specifically, there are devices in the art whereby a solenoid is used to lock an arm of a vacuum signature feeding device in a position of inoperability. Thus, even though the vacuum control continues to function on an intermittent basis in time with the operation of the binding line, the vacuum signature feeding device is prohibited from reciprocating between the associated hopper or pocket where the signatures are stacked and, e.g., the saddle chain or conveyor. In other instances, the vacuum signature feeding device is temporarily disabled by very simply interrupting vacuum thereto.
In the latter case, it has been found that the stack of signatures is loosened by reason of the repeated contact of the device with the signatures in the stack. Thus, when the vacuum is again resumed, the vacuum signature feeding device will have a tendency to pull several of the loose signatures toward the saddle chain or conveyor which is undesirable inasmuch as it may cause a jam in the packer box or a defective book. For this reason, vacuum interruption has been found to be less than entirely satisfactory in the binding line field.
As for locking the vacuum signature feeding device in position with a solenoid, this has found somewhat more wide ranging acceptability. Nevertheless, the mechanical assemblies required for operation of such devices and their associated locking arms and the like have been complex, expensive and less than entirely effective inasmuch as timing can be adversely affected. In this connection, the device is typically disabled by means such as lifting a cam follower from contact with a cam.
The present invention is directed to overcoming the above stated problems and accomplishing the resulting objectives.